Why varietal properties of fruit trees do not change when propagated by grafting?

This is vegetative propagation, and therefore genetic, the material is found only in somatic cells, they are divided by mitosis, with mitosis, the material is copied exactly the same as in the mother cell.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.